This is a multicenter, randomized, double-blind, placebo-controlled study to evaluate the safety, tolerability, PK, and immunogenicity of APG777 in adult participants with mild-to-moderate asthma.

The duration of the study will be approximately 52 weeks (364 days) for each participant and will consist of a Screening Period, Treatment Period, and Follow-up Period.

Inclusion Criteria:

• Have a diagnosis of mild-to-moderate asthma (Global Initiative for Asthma 2023 criteria) ≥ 1 year prior to Screening
• Maintain FeNO-high (≥ 25 parts per billion [ppb]) or FeNO-low (< 25 ppb) status from Screening to Day 1 prior to Randomization
• Pre-bronchodilator forced expiratory volume in 1 second (FEV1) ≥ 60% of predicted normal value at Screening
• Asthma Control Test (ACT) score > 19 at Screening
• Maintained control on as-needed short-acting beta-agonist (SABA) +/- stable dose inhaled corticosteroids (ICS) or stable dose of ICS/ long-acting beta-agonist (LABA); +/- stable dose leukotriene receptor antagonist (LTRA). ICS dose should be stable for ≥ 12 weeks prior to Day 1, LTRA dose should be stable for ≥ 8 weeks prior to Day 1
• Women of childbearing potential and male participants to use a highly effective form of contraception

Exclusion Criteria:

• Any asthma exacerbation requiring systemic corticosteroids within 12 weeks of Screening and/or any asthma exacerbation that resulted in overnight hospitalization within 6 months prior to Screening
• Any history of life-threatening asthma, defined as an asthma episode that required intubation and/or was associated with hypercapnia
• History of biologics use for treatment or control of asthma
• Current smokers or participants with a smoking history of ≥ 10 pack years
• Known history of illicit drug abuse, harmful alcohol use

Note: Other protocol defined criteria may apply.